Computer Aided Process Planning (CAPP) is a generic name for a diverse range of techniques which can be used to take design information for parts, such as engineering components, and create therefrom an appropriate manufacturing route in the form of a set of manufacturing operations which can be used to process raw material in order to produce a desired part. CAPP can be considered to represent an exercise in decision making. The level of human intervention, the extent of the freedom allowed to the computer, the accuracy of any evaluations or simulations the computer is required to run, the acceptable run-time, and the form and extent of the information required by the computer are matters for the CAPP programmer and other decision makers to decide.
The manufacturing methodology used for many intricate and/or high performance parts such as, for example, components of gas turbine engines or the like often involves the formation of a precursor volume via one of a number of possible forming manufacturing processes (e.g. casting and forging). The precursor part produced by the chosen manufacturing process will often be somewhat larger than the desired final shape of the part, and so further processing will then be required (e.g. chip forming operations) to achieve the final desired shape. As will be appreciated, the precursor shape which might be achievable by one manufacturing process will often be somewhat different to that which might be achievable by another manufacturing process.
As will therefore be appreciated, the manufacturing operations which are required to produce any given part will depend on the geometry of the finished part and the shape of the precursor part. It is therefore useful to be able to rapidly estimate the precursor shape which can be created by whatever forming process (e.g. casting or forging) is to be used. In order to optimise the process and cost modelling, it is important to be able to estimate a precursor shape automatically.
It has been previously proposed to estimate a precursor shape via the use of a full rule-based technique, which has been found to be accurate and to require a mid-level of computational complexity. However, this technique is not generic to all part shapes and so requires the formation of a different set of rules for each different part. A different set of rules is also required for each manufacturing process.
It has also been previously proposed to create a precursor shape simply by adding an offset of a few millimeters around the final desired part shape, optionally including the use of a smoothing algorithm or taking account of sharp corners. However, these techniques are considered to be far from optimal.